Voltage control system



A. H. MITTAG ET AL VOLTAGE CONTROL SYSTEM Filed July 22, 1950 AMPERE TURNS PEfamcH b un HBL PUMO Fzmukml ERE AMF

TURNS `une 10, 1952 lnventors. Albert r-LMttagg, Marvin JMuIherrw, by @4m Their/Attorney Patented June 10, 1952 UNITED STATES PATENT FFICE- VOLTAGE GONTRQLAv SYSTEM:

Albert H.- Mittag and Marvin J^.Mulh ern, Schrenectady, N, Y., assignors to (rveneral-k Electric Company, a corporation of Nevv York AppliatonJuly 22, 1950, Serial No. 175,450

9 Claims. 14

This-y invention relates to: voltage4 control systems and more particularly to an arrangement for maintaining the output voltage of an electronic translating system substantially constant even thoughthe supply voltage-varies over-a relatively wide range.

Where direct current motors are energized from electronic rectifying apparatus such as` ignitron tubes,- ior example, it is desirable to avoid iluctuations in the Voltage supplied by the electronic translating apparatus even though the voltage or frequency of the alternating-current circuits associated With the electronic equipment is subject to substantial variations.

Electronic valves of theVV ignitron type` having an anode, a control grid, a holding anode and a mercurypool cathode enclosed in an envelope utilize anignitor element immersed in the mercuryy poolto establish a cathode spot within the valve when a current is supplied through the ignitor element. Itis wellknown that the output of'such valves can be controlled by either controlling theenergizationofv the control grid or-by controlling the phase angleof the energization of the ignitor firing circuit relative to the cathodeanode voltage of the valve.

In known rectifyingv equipment-utilizing ignitrons it'hasbeen the practice to control the phase angle ofthe ignitorcircuit-by suitable phaseV control means energized from an alternating current source. Because such phase shifting control means as WellY asthe ignitor ringcircut itself are inherentlysensitive to fluctuations in the a1-I ternating current supply voltage and hence tend toproduce. unreliable operating.characteristics ofv the valves, ithasbeen the practice to usea relatively. expe'nsive,constant-voltage transformer for maintalningoay substantiallyconstant/voltage supply to thephase control means even though the voltage of f the` alternatingv current sourcey might vary considerably.

A principal object o-f the-,invention is to provide an improved voltage regulating system for electronic translating apparatus.

Another object of* theinvention is toprovide anr improvedcontrol arrangement for electronic translating equipment whereinvariations in the supply voltage. are utilized-to aid` in controlling the outputvoltager Still; another object of the. irmention is to provide an improved` control arrangement forfelec- QP-i9 tratl: eqllpmnl" Whrllzfvallil in.l thooopply, frequency oro utilized.4 to aol. io oootrollios thoollootvoltoso,

A further object.v of the invention is` the; pro` vision of. oo. imorovod ohooo ControlV System for controlling a control element of an electronic valve without the necessity forusing arelatively expensive oonstontivoltaso transformer..

Accordine@y to thev invention the phase anglo/of an ignitor iiring circuit for van ignitron tube; is controlled by an amplistat or magnetic amplifier circuithaying mainwindings and a biasing winding energized directly from a source of alternatingA current voltagewhich voltage is subject to variations. A feedbacky Winding for the amplistat is responsive to the output voltage of: the systemand controlV ofthe circuit is obtained by means fo a control Winding for the amplistat arranged'to beenergized by an adjustablebut'relatively stable current source. Thus, when adesiredadjustment of the output voltage is estab lished through the agency of the control Winding such voltage is maintained substantially con- Stant through the action of the feedback, bias-.- ing andV control windings whichy together produce a magnetizing action suicient to render theiamplistateectivein automatically controlling the phase oftheignitor circuit and thereby to maintain the output voltage of the. valve,v subsequently constant even though the supply voltage. may change.

For a better understanding of the invention reference may be had to the accompanyingdrawings in which Fig. 1 is a schematic representation of translating apparatus of theV electronic typein Which my invention is embodied; Fig. 2 is av family or curves toaid in understandingsome of the principles of the invention; and Fig. 3 is a schematic representation of a modification of Fig. 1;

While the arrangement shown in Fig. 1 andl to be described hereinafter is a rectifying system, it will be understood that the invention isalso applicable to` an inverter system as will beex-A plained.

With reference to Fig. 1 the alternating, current circuit comprising conductors I and` 2 sup--A plied energy toV be rectified and fedto the direct current;4 circuit comprising conductors 3V and 4,. Energy from the alternating current circuit is supplied through circuit breakers 5` and. (i and transformer l to ignitron tubes 8 and 9. Each of the tubes 8 and 9 is provided with a control-grid i0, a holding anode Il; a cathode l2 comprising a mercury pool, andan ignitor element I 3. Valves 8 and` 9 are arranged to conduct alterna-te halfe, cycles of alternating current energy suppliedfrom the-alternating currentl circuit.

Ignitors I 3- are energized through the. firing circuit` comprising transformer I4 energized from thealternating current sourcev Whichin turn en-` el'gizes the ignitor coupling transformer IC'I' which in turn supplies current throughl unidif rectional conducting device FMR-l tol the; igf nitor of tube 8l and through unidirectional conducting deviceFMR-Z to the ignitor of tube 9; As is well kknown acharge supplied through linear reactor LL accumulates on firing capacitory andfsubsequentlygis discharged through firingfref.

actor FL into the primary winding oi transformer ICT. Phase shift is accomplished in part by the action of phase shifting reactor CL and phase shifting capacitor PC in a manner well known in the art. Controllable phase shifting is accomplished by phase shifting device I5 having a main winding I6 and a control winding I1. As is Well known variations in the ow of current through winding l1 will effect a shift in phase in the current supplied to ignitor elements I3.

For controlling the flow of current through winding I1 the amplistat or magnetic amplifier generally designated by the numeral IS is used. Amplistat I8 comprises a main winding I9 and another main winding 23. Ordinarily the windings I9 and 20 would be respectively wound on thin individual magnetic cores which for convenience could be provided with a common supporting means. Unidirectional conducting devices 2I and 22 are associated with main winding I8 while unidirectional conducting devices 23 and 24 are associated with main winding 2S. Devices 2I--24 preferably should be selenium type rectiers. Energy is supplied to the amplistat from the alternating current circuit through conductors 25 and 2S and output from the amplistat is supplied to winding I1 through conductors 21 and 28 and resistor 29. Thus when conductor 2 for example is positive, current will flow through conductor 25 downwardly in main winding 2li through conductor 21, winding I1, device 22 and conductor 26 to conductor I. When conductor I is positive current iiows through conductor 2S, device 24, conductor 21, resistor 29 winding I1 upwardly through winding I9. device 2 I, and conductor 25 to conductor 2.

As is well known the magnetic condition or degree of saturation of the iron of amplistat I3 determines the impedance of the amplistat and hence determines the magnitude of current iiow through control winding I1.

For the purpose of controlling the degree of magnetization of the amplistat I8 at least to some extent, a winding such as 30 is used. Winding 30 is a control winding magnetically coupled with both the main windings IB and 2e and energized through adjustable device 3|, rectiiiers 32, and constant voltage transformer CVT from the source of alternating current. Since the transformer CVT supplies constant voltage irrespective of whether the voltage of the alternating current supply varies, the value of the current Ie which flows through winding 30 is determined by the adjustment of the device 3I, Hence device 3l and control winding 3D comprises a means for establishing an operating range for the device. In Fig. 2 the magnetizing eifect of the current Ic is represented by the horizontal vector labeled Ic. Ordinarily the direction of flow of the current Ic would be such that the magnetizing eiiect of this current would aid the magnetizing effect of the current owing through main windings I9 and 20 of the amplistat I8.

For the purpose of rendering the amplistat I8 responsive to changes in voltage of the alternating current circuit a biasing winding 33 is used. Winding 33 is magnetically coupled with main windings IS and 2B and is energized through adjustable device 24, rectiers 35 and transformer BT which in turn is energized from the alternating current source. Thus changes in the voltage of the alternating current source will result in changes in the current owing to the winding 33 since transformer BT is not a constant voltage device as in known arrangements.

Ordinarily the winding 33 would be arranged so that the flow of the current It therethrough would exert a biasing action which would be opposed to the biasing action of the current flowing through control winding Si) and the main windings I9 and 29. In 2 the magnetizing eiect of this biasing current is represented by the vector Ie.

In order that the amplistat IS will be responsive to voltage changes in the direct current output circuit comprising the conductors 3 and 4, a feedback winding 36 of amplistat I8 is connected in series with a suitable resistor r so to be energized by the voltage appearing acrose the direct current output circuit. Feedback winding 3G, like control winding 30 and biasing winding 34, is magnetically coupled with main windings I 9 and 20. Normally, the magnetizing eiieot of the feedback current Ifb in the winding 36 would be such as to aid the magnetizing effect of the biasing winding 33 and to oppose the magnetizing effect of the control winding 3c. In Fig. 2 the magnetomotive force due to thc current Ifb is represented by the vector labeled Ifb. Thus the feedback winding 33 and the biasing winding 36 tend to demagnetize the iron of the amplistat I8 when a voltage in excess of the desired value occurs on the alternating and direct current circuits.

In Fig. 2 the per cent output voltage of the rectifier circuit is plotted against the net ampere turns resulting from the magnetizing effect of the currents It, Ic, and Im. This value of net ampere turns is the value for a normal or 100% value of voltage of the alternating current circuit comprising conductors I and 2. Curve A of Fig. 2 is representative of the voltage conditions for normal operation. Curve B is representative ol some value of voltage of the alternating current circuit less than the normal value such as f/- while curve C is representative of a voltage condition of the alternating current circuit in excess of the normal voltage value such as 110%. In Fig. 2 the vertical dotted lines indicate the magnitude of the bias due to the current Ib for tbrcc values of the alternating current voltage.

The three curves of Fig. 2 represent three voltage conditions in the alternating current circuit. Voltage changes in the alternating current, circuit eiect changes in the characteristics of the firing circuit, in the characteristic of the amplistat, and in the characteristics of the phase shifting circuit comprising device l5, reactor CL, and capacitor PC. Thus, a reduction in the alternating current voltage from its normal value to its 85% value for example, effects changes in the characteristic shown in Fig. 2 to the extent of changing the characteristic from that represented by curve A to that represented by curve B. Such a reduced voltage would result in a reduction in the magnitude of the bias current Ib. Since a reduction in the alternating current voltage would also result in some reduction at least momentarily in the direct current voltage, the value of the feedback current In; Will also be reduced. Since the value of the control current Ic remains unchanged the net ampere turns will be reduced. Such a reduction in the magnetomotive force applied to the amplistat due to a reduction of the biasing and feedback currents Will tend to decrease its impedance and in turn to increase the magnitude of the current flowing through the winding I1 since the control current is unchanged. An increased current through the winding I1 will have the -eect of advancing .the nring point of the ignitcrs I3`so'as to increase the voltage of the direct current output circuit comprising conductors 3 and 4. Thus by the'invention it will be seen that a large relatively expensive constant yvoltage transformer is not needed for the purpose of energizing the main windings I9 and 2i! ofthe amplistat I8 nor is such a transformer yneeded for the purpose of energizing a biasing winding such as 33. By the invention it is possible to energize the main windings of the amplistat I8 directly from the alternating current circuit. Furthermore the relatively inexpensive biasing transformer BT can be used and the variations in voltage produced thereby .can be effectively utilized to aid in proper voltage control.

It will be understood that the arrangement comprising the invention is also applicable to an arrangement such as that shown in Fig. 1 when operated as an inverter.

The arrangement already described can `be made frequency responsive by merely substituting the circuit shown in Fig. 3 for that portion of Fig. 1 enclosed by dotted lines. to Fig. 3, a resistor R, a capacitor C and a reactor L are connected across the transformer BT. Rectiiier 35 is energized from the frequency responsive circuit comprising R, L, and C through a transformer FT. Suitable constants would be chosen for R, L, and C to accomplish the desired control of amplistat I3. For certain applications it might be possible to dispense with transformer FT and to energize rectiiiers 35 directly from a portion of the frequency responsive circuit comprising RL and C. Of course it might be desirable to use voltage responsive as well as frequency responsive means in a particular application of the invention.

It will be apparent to those skilled in the art that the invention is not limited to the particular arrangement shown and described but that changes and modifications may be made without departing from the spirit and scope of the invention and it is intended that the appended claims Will cover all such changes and modiiications.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. In combination, an alternating current circuit, a direct current circuit, electric valve means having an anode, a cathode, and a control member interposed between said circuits, control means for energizing said control member so as to render said valve means conductive periodi cally, phase shifting means including a direct current control winding for varying the phase angle of the energization of said control member relative to the voltage of said anode and said cathode, ainplistat means having main windings energized from a source of alternating current voltage and arranged in series with unidirectional conducting devices to supply direct current to said direct current control winding of said phase shifting means, a control winding for said ainplistat, adjustable means for energizing said control winding with predetermined polarity, a biasing winding for said amplistat, means for energizing said biasing winding from one of said circuits so that the biasing effect thereof is dependent upon the voltage of said circuit, and a feedback winding on said amplistat energized in accordance with the voltage of the other of said circuits.

2. In combination, an alternating current cir- With reference i cuit, a direct current circuit, electric valve means having an anode, a cathode, and a control member interposed between said circuits, a control circuit for energizing said control member so as togrender said valve means conductive periodically, phase shifting means including a direct current control winding for varying the phase angle of the energization of said control circuit relative to the voltage of said anode and cathode, amplistat .means having main windings energized from a source of alternating current voltage and arranged in series with unidirectional conducting devices to supply direct current to said direct current control Winding of said' phase shifting means, a controlwinding for said amplistat, adjustable means for energizing said control winding with predetermined polarity, a biasing winding for said amplistat, means for energizing said biasing winding from said alternating current circuit so that the biasing effect thereof is dependent upon a predetermined electrical quantity of said alternating current circuit, and a feedback winding on said amplista't energized in accordance with the voltage of said direct current circuit, the magnetizing action of said biasing Winding and said feedback Winding being in opposition to the biasing action of said control winding.

3. In combination, an alternating currentsupply circuit, a direct current load Circuit, electric valve means having an anode, a cathode, and a control member interposed between said circuits, a control circuit for energizing said control member so as to render said valve means conductive periodically, phase shifting means including direct current control winding for varying the phase angie of the energization of said control member relative to the voltage of said anode and cathode, amplistat means having main windings energized irorn a source of alternating current voltage and arranged in series with unidirectional conducting devices to supply direct current to said directcurrent control winding o said phase shifting means, a control winding for said amplistat, adjustable means for energizing said control winding with predetermined polarity, a biasing winding for said ampistat, means for energizing said biasing winding from said supply circuit so that the biasing effect thereof is dependent upon a predetermined electrioal quantity of said supply circuit, and a feedback winding on said amplistat energized in accordance with the voltage of said load circuit.

a. In combination, an alternating current supply circuit, a direct current load circuit, electric valve means having an anode, a cathode, and a control member interposed between said circuits, a control circuit for energizing said control member so as to rende; said valve means conductive periodically, phase shifting means including a direct current control winding for varying the phase angle of the energization or" said control member relative to the voltage of said anode and cathode, amplistat means having main windings energized from a source of alternating current voltage and arranged in series with unidirectional conducting devices to supply direct current to said direct current control winding of said phase shifting means, a control winding for said amplistat, adjustable means for energizing said control winding with predetermined polarity, a biasing winding for said amplistat, means for energizing said biasing Winding from said supply circuit so that the biasing effect thereof is dependent upon the voltage of said supply circuit, and a feedback winding on said amplistat energized in accordance with the voltage of said load circuit.

,5. In combination, an alternating current supply circuit, a direct current load circuit, electric valve means having an anode, a cathode, and a control member interposed between said circuits, a control circuit for energizing said control member as to render said valve means conductive periodically, phase shifting means including a direct current control winding for varying the phase angle of the energisation of said control membe relative to the voltage of said anode and cathode, a-mplistat means having main windings energized from a source of alternating current voltage and arranged in series with unidirectional conducting devices to supply direct current to said direct current control winding of said phase shifting means, a control winding for said amplistat, adjustable means for energizing said control winding with predetermined polarity, a biasing winding for said ampiistat, means for energizing said biasing winding from said supply circuit so that the biasing effect thereof is dependent upon the frequency oi said supply circuit, and a feedbaci: winding on said amplistat energized in accordance with the voltage of said load circuit.

6. In combination, an alternating current supply circuit, a direct current load circuit, electric valve means having an anode, a cathode and a .control member interposed between said circuits, a control circuit for energizing said control member so as to render said valve means conductive periodically, phase sluiting means including a direct current control winding for varying the angle between the time of energization of sai-:l control circuit relative to the voltage of said anode and cathode. amplistat means having main windings energized from said alternating current supply circuit and arranged in series with unidirectional conducting devices to supply direct current to said direct current control winding of said phase shifting means, a control 'winding for said amplistat, adjustable means for energizing said control winding with predetermined polaria biasing winding for said amplistat, means for energi ing said biasing winding from said supply circuit so that the biasing effect thereof is dependent upon the voltage of said supply circuit, and a feedback winding on said ainplistat energized in accordance with the voltage of said load circuit, the magnetizing action of said control winding being eiectivc to aid the magnetizing action of the circuit through said main windings.

7. In combination, an alternating current supply circuit, a direct current load circuit, electric valve means having an anode, a mercury pool cathode and an ignitor interposed between said circuits, a control circuit for energizing said ignitor, phase shifting means including a direct current control winding for controlling the energization of said control circuit relative to the voltage of said anode and cathode, amplistat means having main windings energized from a source of alternating current voltage and connected in series with rectifying means to supply direct current to said direct current control winding of said phase shifting means, a control winding for said amplistat, adjustable means for energizing said control winding with a predetermined Value of control current, a biasing winding for said amplistat, means for energizing said biasing Winding from said supply circuit so that the biasing eiect thereof is dependent upon the voltage of said supply circuit, and a. feedback winding on said amplistat energized in accordance with the voltage of said load circuit.

8. In combination, an alternating current supply circuit, a direct current load circuit, electric valve means having an anode, a cathode and a control member interposed between said circuits, a control circuit for periodically energizing said control member, phase shifting means including a direct current control winding for varying the periodic energization of said control circuit relative to the voltage of said anode and cathode, amplistat means having main windings energized from a source of alternating current voltage and arranged in series with unidirectional conducting devices to supply direct current to said direct current control winding of said phase shifting means, a control winding for said amplistat, adjustable means for energizing said control winding with a predetermined value or" direct current, a biasing winding for said amplistat, transformer and rectifying means for energizing said biasing Winding with direct current from said supply circuit so that the biasing effect thereof is dependent upon the voltage of said supply circuit, and a feedback winding on said amplistat energized in accordance with the voltage of said load circuit.

9. ln combination, an alternating current supply circuit, a direct current load circuit, electric valve means having an anode, a cathode and a control. member interposed between said circuits, a control circuit for energizing said control member, phase shifting means including a direct current control winding for varying the energizetion of said control circuit relative to the voltage of said anode and cathode, ainplistat means having main windings connected in series with rectifying means and energized from a source of alterhating current voltage for supplying direct current to said direct current control winding of said phase shifting means, said main windings being connected to conduct alternate half cycles of current from said source, a control Winding for said amplistat, adjustable means for energizing said control winding with a predetermined value of control current, a biasing winding for said amplistat, means for energizing said biasing winding from said supply circuit so that the biasing effect thereof is dependent upon the voltage of said supply circuit, means for adjusting the biasing action of said biasing winding, and a feedback winding on said amplistat energized in accord.- ance with the voltage of said load circuit, the magnetizing action of said feedback and biasing windings being in opposition to the magnetizing action of said control Winding and said main windings.

ALBERT H. MITTAG. MARVIN J. MULHERN.

REFERENCES ClTED The following references are of record in thc iile of this patent:

UNITED STATES PATENTS Number Name Date 2,103,997 Bedford Dec. 28, 1937 2,126,790 Logan Aug, 16, 1938 2,128,771 Forssell et al Aug. 30, 1938 2,186,244 Hartel Jan. 9, 1940 2,193,649 Schmidt Mar. l2, 1940 2,349,633 Meyers May 23, 1944 2,435,187 Bedford Feb. 3, 1948 

